769 research outputs found
Particle-Hole Spectral Asymmetry at the Edge of Multi-orbital Noncentrosymmetric Superconductors
Bogoliubov quasiparticles are coherent electron-hole quantum superposition
which typically, for time-reversal symmetric superconductors, exhibit a
spectral distribution with particle-hole symmetry. Here, we demonstrate that in
two-dimensional noncentrosymmetric superconductors with inter-orbital -wave
spin-triplet pairing the energy profile of the density of states at the edge
violates this paradigm. We unveil the spin-orbital structure of multiple
Andreev reflections and how these processes lead to anomalous septet pairing
states built out of mirror symmetric quasiparticles, a configuration that is
symmetry prohibited in the bulk. The resulting edge-bulk pairing mismatch is
the origin of the asymmetric peaks for the spectral function. Remarkably, the
distribution of the asymmetric line shape can be controlled by designing the
spatial profile of the inversion symmetry breaking interaction. These findings
can qualitatively account for the phenomena observed at the surface of the
UTe superconductor and be exploited to single out the nature of pairing at
oxide interface superconductors.Comment: 7 pages, 3 figures, and 3 pages, 5 figures in supplemental materials.
Comments are welcom
The zinc finger transcription factor PW1/PEG3 restrains murine beta cell cycling
Aims/hypothesis: Pw1 or paternally-expressed gene 3 (Peg3) encodes a zinc finger transcription factor that is widely expressed during mouse embryonic development and later restricted to multiple somatic stem cell lineages in the adult. The aim of the present study was to define Pw1 expression in the embryonic and adult pancreas and investigate its role in the beta cell cycle in Pw1 wild-type and mutant mice.
Methods: We analysed PW1 expression by immunohistochemistry in pancreas of nonpregant and pregnant mice and following injury by partial duct ligation. Its role in the beta cell cycle was studied in vivo using a novel conditional knockout mouse and in vitro by lentivirus-mediated gene knockdown.
Results: We showed that PW1 is expressed in early pancreatic progenitors at E9.5 but becomes progressively restricted to fully differentiated beta cells as they become established after birth and withdraw from the cell cycle. Notably, PW1 expression declines when beta cells are induced to proliferate and loss of PW1 function activates the beta cell cycle.
Conclusions/interpretation: These results indicate that PW1 is a co-regulator of the beta cell cycle and can thus be considered a novel therapeutic target in diabetes
The lack of star formation gradients in galaxy groups up to z~1.6
In the local Universe, galaxy properties show a strong dependence on
environment. In cluster cores, early type galaxies dominate, whereas
star-forming galaxies are more and more common in the outskirts. At higher
redshifts and in somewhat less dense environments (e.g. galaxy groups), the
situation is less clear. One open issue is that of whether and how the star
formation rate (SFR) of galaxies in groups depends on the distance from the
centre of mass. To shed light on this topic, we have built a sample of X-ray
selected galaxy groups at 0<z<1.6 in various blank fields (ECDFS, COSMOS,
GOODS). We use a sample of spectroscopically confirmed group members with
stellar mass M >10^10.3 M_sun in order to have a high spectroscopic
completeness. As we use only spectroscopic redshifts, our results are not
affected by uncertainties due to projection effects. We use several SFR
indicators to link the star formation (SF) activity to the galaxy environment.
Taking advantage of the extremely deep mid-infrared Spitzer MIPS and
far-infrared Herschel PACS observations, we have an accurate, broad-band
measure of the SFR for the bulk of the star-forming galaxies. We use
multi-wavelength SED fitting techniques to estimate the stellar masses of all
objects and the SFR of the MIPS and PACS undetected galaxies. We analyse the
dependence of the SF activity, stellar mass and specific SFR on the
group-centric distance, up to z~1.6, for the first time. We do not find any
correlation between the mean SFR and group-centric distance at any redshift. We
do not observe any strong mass segregation either, in agreement with
predictions from simulations. Our results suggest that either groups have a
much smaller spread in accretion times with respect to the clusters and that
the relaxation time is longer than the group crossing time.Comment: Accepted for publication in MNRA
Protein signatures of centenarians and their offspring suggest centenarians age slower than other humans
Using samples from the New England Centenarian Study (NECS), we sought to characterize the serum proteome of 77 centenarians, 82 centenarians\u27 offspring, and 65 age-matched controls of the offspring (mean ages: 105, 80, and 79 years). We identified 1312 proteins that significantly differ between centenarians and their offspring and controls (FDR \u3c 1%), and two different protein signatures that predict longer survival in centenarians and in younger people. By comparing the centenarian signature with 2 independent proteomic studies of aging, we replicated the association of 484 proteins of aging and we identified two serum protein signatures that are specific of extreme old age. The data suggest that centenarians acquire similar aging signatures as seen in younger cohorts that have short survival periods, suggesting that they do not escape normal aging markers, but rather acquire them much later than usual. For example, centenarian signatures are significantly enriched for senescence-associated secretory phenotypes, consistent with those seen with younger aged individuals, and from this finding, we provide a new list of serum proteins that can be used to measure cellular senescence. Protein co-expression network analysis suggests that a small number of biological drivers may regulate aging and extreme longevity, and that changes in gene regulation may be important to reach extreme old age. This centenarian study thus provides additional signatures that can be used to measure aging and provides specific circulating biomarkers of healthy aging and longevity, suggesting potential mechanisms that could help prolong health and support longevity
The Milky Way Tomography With SDSS. III. Stellar Kinematics
We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r 20 degrees). We find that in the region defined by 1 kpc < Z < 5 kpc and 3 kpc < R < 13 kpc, the rotational velocity for disk stars smoothly decreases, and all three components of the velocity dispersion increase, with distance from the Galactic plane. In contrast, the velocity ellipsoid for halo stars is aligned with a spherical coordinate system and appears to be spatially invariant within the probed volume. The velocity distribution of nearby (Z < 1 kpc) K/M stars is complex, and cannot be described by a standard Schwarzschild ellipsoid. For stars in a distance-limited subsample of stars (< 100 pc), we detect a multi-modal velocity distribution consistent with that seen by HIPPARCOS. This strong non-Gaussianity significantly affects the measurements of the velocity-ellipsoid tilt and vertex deviation when using the Schwarzschild approximation. We develop and test a simple descriptive model for the overall kinematic behavior that captures these features over most of the probed volume, and can be used to search for substructure in kinematic and metallicity space. We use this model to predict further improvements in kinematic mapping of the Galaxy expected from Gaia and the Large Synoptic Survey Telescope.NSF AST-615991, AST-0707901, AST-0551161, AST-02-38683, AST-06-07634, AST-0807444, PHY05-51164NASA NAG5-13057, NAG5-13147, NNXO-8AH83GPhysics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA) PHY 08-22648U.S. National Science FoundationMarie Curie Research Training Network ELSA (European Leadership in Space Astrometry) MRTN-CT-2006-033481Fermi Research Alliance, LLC, United States Department of Energy DE-AC02-07CH11359Alfred P. Sloan FoundationParticipating InstitutionsJapanese MonbukagakushoMax Planck SocietyHigher Education Funding Council for EnglandMcDonald Observator
The structure and emission model of the relativistic jet in the quasar 3C 279 inferred from radio to high-energy gamma-ray observations in 2008-2010
We present time-resolved broad-band observations of the quasar 3C 279
obtained from multi-wavelength campaigns conducted during the first two years
of the Fermi Gamma-ray Space Telescope mission. While investigating the
previously reported gamma-ray/optical flare accompanied by a change in optical
polarization, we found that the optical emission appears delayed with respect
to the gamma-ray emission by about 10 days. X-ray observations reveal a pair of
`isolated' flares separated by ~90 days, with only weak gamma-ray/optical
counterparts. The spectral structure measured by Spitzer reveals a synchrotron
component peaking in the mid-infrared band with a sharp break at the
far-infrared band during the gamma-ray flare, while the peak appears in the
mm/sub-mm band in the low state. Selected spectral energy distributions are
fitted with leptonic models including Comptonization of external radiation
produced in a dusty torus or the broad-line region. Adopting the interpretation
of the polarization swing involving propagation of the emitting region along a
curved trajectory, we can explain the evolution of the broad-band spectra
during the gamma-ray flaring event by a shift of its location from ~ 1 pc to ~
4 pc from the central black hole. On the other hand, if the gamma-ray flare is
generated instead at sub-pc distance from the central black hole, the
far-infrared break can be explained by synchrotron self-absorption. We also
model the low spectral state, dominated by the mm/sub-mm peaking synchrotron
component, and suggest that the corresponding inverse-Compton component
explains the steady X-ray emission.Comment: 23 pages, 18 figures 5 tables, Accepted for publication in The
Astrophysical Journa
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